blinn phong lighting creating strange results - c++

Question

I'm creating a raycaster and trying to use global illumination as a shading method
I've calculated the intersect of a a sphere and cube as well as their normals
creating each of the separate ambient, diffuse and specular result in shading the object as expected however
overall once adding them together as shown in the code below
glm::vec3 n = surfaceNormal(position, intersect);
glm::vec3 lightStart = glm::vec3(-10, 1, 10);//light points in 3d space
glm::vec3 lightDir = glm::normalize(lightStart - intersect); // direction towards light source
glm::vec3 viewDir = glm::normalize(cam.pos - intersect); // direction towards camera
glm::vec3 midDir = glm::normalize(lightDir + viewDir);//mid point between light and view
glm::vec3 lightColor = glm::vec3(1, 1, 1);//color of light
glm::vec3 objectColor = color ;
float shinyness = 10.0f;
float ambientStr = 0.1f;
///ambient
glm::vec3 ambient = lightColor * ambientStr;
///diffuse
glm::vec3 diffuse = lightColor * glm::max(glm::dot(n,lightDir), 0.0f);
///specular
//ks * light color * facing * (max(n dot h))
glm::vec3 specular = lightColor * facing(n, lightDir) *
std::pow(glm::max(glm::dot(n, midDir), 0.0f), shinyness);
glm::vec3 outColor = ambient + diffuse + specular;
return outColor * objectColor * 255.0f;
the facing method returns 1 if the cross product of (n,lightDir) > 0 else it returns 0
this is to avoid lighting faces pointed in the wrong direction
this is the result:

Answer 1

The *255f was suspicious already (typical usage of OpenGL works with color components in the range of [0...1]), and you added a comment
the output are float values for color being drawn straight to screen.
It is a simple overflow issue then. Your weight is a sum of 0.1+[0...1]+[0...1] (ambient, diffuse and specular), which falls into [0.1 ... 2.1], and when you multiply it with a color component larger than 0.5 (approximately, 1/2.1 is the precise limit), their product exceeds 1. Then this number is multiplied with 255, and the result will be above 255, and when truncated to a byte, it "starts over" from black, component-wise.
Based on the code you show, you could probably try something like
return glm::min(outColor * objectColor * 255.0f, glm::vec3(255f, 255f, 255f));
but there may be a better function for that.